1. Field of the Invention
This invention relates to a method for preparing organopolysiloxanes. More particularly, this invention relates to a method for preparing alpha, omega-perfluoroalkylethylmethylpolysiloxanes where the perfluoroalkyl portion of the substituent contains more than one carbon atom.
2. Background Information
The preparation of halogen-terminated siloxanes by reaction of the corresponding halosilane R.sub.n SiX.sub.4-n with zinc oxide is taught in U.S. Pat. No. 2,629,726, which issued to Hyde on Feb. 24, 1953. X represents halogen and the only halogenated hydrocarbon radicals represented by R are halogenated aryl, as exemplified by trifluorotolyl.
The preparation of hexaphenylcyclotrisiloxane, a cyclic trimer, by the reaction of diphenyldichlorosilane and zinc oxide in methyl acetate conducted at the boiling point the reaction mixture is described in the Journal of Organic Chemistry, Volume 25, Number 2, pp. 310-311 (1960).
It is known that the hydrolysis of a dialkyldichlorosilane produces a mixture of cyclic oligomeric dialkylsiloxanes and the corresponding linear dialkylpolysiloxane. The linear dialkylpolysiloxane can in many instances be recovered by distillation of the lower boiling cyclic oligomeric dialkylsiloxanes from the reaction mixture. However, in the case of perfluoroalkylethylmethylpolysiloxanes containing more than one carbon atom, the high boiling points of the corresponding cyclic oligomeric dialkylsiloxanes essentially preclude their separation by distillation.
One objective of the present invention is to provide a method for preparing alpha, omega-dihydroxyperfluoroalkylethylmethylpolysiloxanes that generates this product in high yields in the substantial absence of the corresponding cyclic oligomers.